The present invention relates to a structural member with aligning means for a mating part, and more particularly to a rigid body formed of a hard material having at least one hole therein for receiving a mating part formed of a material such as wood which is softer than the material of the body. The hole includes alignment means for properly aligning the mating part relative to the body.
The invention is especially adapted for use with pieces of wood such as conventional "2.times.4 lumber", wherein the lumber has a rectangular cross-section. The rigid body may comprise a component of shelving utilizing 2.times.4 lumber such as disclosed in U.S. Design patent application Ser. No. 29/103,042, the disclosure of which is incorporated herein by reference. The rigid body may also comprise a component of a convertible bench and table top assembly as disclosed in U.S. Pat. No. 4,913,488, the disclosure of which is incorporated herein by reference. The invention can be employed in other types of construction wherein it is desired to interconnect a rigid body with a mating part which is formed of material which is softer than that of the rigid body.
The original design of the rigid body for use with shelving is disclosed in U.S. Design patent application Ser. No. 29/091,633, the disclosure of which is incorporated herein by reference. In this original design, rectangular holes were provided which were oversized for receiving pieces of lumber therein which were secured in place by screws. It is common knowledge that lumber, while milled to a specific dimensional size, does not maintain its dimensions and shape when exposed to the environment, resulting in the lumber swelling, bowing, twisting and cupping. The oversized rectangular holes were intended to provide clearance for the changes in size and shape of the lumber which occurs in the normal course of events, without introducing stress into the rigid body. The rigid body and piece of lumber were assembled by the use of a single screw extending through one long side of a hole and a single screw extending through one short side of a hole, effectively pulling the lumber into contact with the sides of the hole forming one corner of the hole, which is similar to the arrangement with other commonly available brackets and the like.
This original design proved to be unacceptable. Since the rigid body may be, for example, either a metallic casting or a molded plastic, it is necessary to provide relief angles or "draft" for the large rectangular openings so that the molded or cast body can be effectively released from the mold. Such relief angles make it difficult to properly align the lumber so that it extends perpendicular to the body as is desired. Furthermore, the average amount of clearance between most lumber and the sides of the holes afforded movement and/or deflection of the non-contacting sides of the lumber, which resulted in twisting and misalignment of the rigid body relative to the lumber. Therefore, the assembled rigid bodies and lumber are not sufficiently stable. This is a common problem with these types of assemblies, and manufacturers often suggest the use of additional components for cross-bracing the assemblies.